This invention relates to mixing, kneading, and processing machinery of the type in which at least two parallel shafts with mating worms or the like thereon are in continuous wiping engagement with the walls of the barrel or vessel through which the shafts extend, and also are in continuous inter-wiping relationship. Machinery of this design, wherein the materials being mixed or processed are subjected to an intense shearing and kneading action as they proceed continuously through the machine, and all product contacting sufraces of the mixer are continuously wiped clean during the operation of the mixer, are well known and used in a variety of processes, particularly where doughy or viscous materials are being processed. Machines of this character have been provided with worms in the form of progressively angularly displaced paddles, either straight or formed on a helix, provided in axially abutting relation on the mixing shafts such as exemplified, for instance, in U.S. Pats. Nos. 3,195,868; 3,387,826; and 3,423,074. Such machines have also been provided with worms in the form of elongate screws as disclosed in U.S. Pats. Nos. 3,900,187; 3,305,894; and 3,698,693, for example. The mixing machines to which I've referred are what may be termed "fixed axis of rotation" machines, but orbiting twin screws have also been proposed, as disclosed in U.S. Pat. No. 3,614,070. U.S. Pat. No. 4,344,711 in a vertical batch mixer discloses a fixed axis of rotation machine wherein helical blades both mutually co-wipe and wipe the wall of the vessel of figure eight cross-section, but leave a central core of material which is not penetrated by the blades. The purpose of the various prior art designs has been to provide some versatility in machines of this character to suit them to homogenously mix and/or knead materials which may be in plastic, liquid, granular, or powder form. The prior art machines have, however, not been found to provide the versatility desired for processing many materials such as processing operations in which light or fibrous materials are to be introduced to a viscous mass and homogenously dispersed therein throughout the whole mass.